1. Field of the Invention
This invention relates to a multilayer glass structure, and more specifically, to a multilayer glass structure which is so constructed as to prevent effectively not only the condensation of water vapor and vapor of an organic solvent in spaces within the glass structure but also the occurrence of dust from an adsorbent included in the glass structure.
2. Description of the Prior Art
A multilayer glass structure constructed by joining the edge portions of a plurality of glass sheets by a sealant through spacers having a dessicant included therein has been used heretofore in various buildings as a windowpane having excellent thermal and acoustic insulating effects.
One problem with this multilayer glass structure is that when the temperature of air in the spaces between the glass sheets decreases to below the dew point, vapors in these spaces are condensed to reduce the visual field of the windowpane. It is known that such vapors include not only water vapor in the air originally existing in the spaces between the glass sheets and water vapor contained in the air leaking through the spaces between the glass sheets and the spacers, but also vapor of an organic solvent which is contained in the sealant and evaporated with the lapse of time.
It is known to use synthetic zeolites, active alumina, silica gel, etc. as dessicants or adsorbents for the adsorption of these vapors. These adsorbents, however, have not proved to be entirely satisfactory for the purpose of absorbing and removing a mixture of water vapor and an organic solvent vapor in such a way as to prevent "fogging" despite a wide range of temperature variations. For example, it is said that among the above-mentioned adsorbents, silica gel is most suitable for the adsorption of an organic solvent vapor. But in a system including both water and an organic solvent, silica gel tends to adsorb water selectively and preferentially, and therefore, its effect is questionable in the adsorption of both.
From this viewpoint, the use of a combination of adsorbents for a multilayer glass structure has already been proposed. For example, Japanese Laid-Open Patent Publication No. 71650/1980 discloses the use of a combination of 3A-type molecular sieve zeolite with hydrocarbon-adsorptive silica gel, active alumina or activated carbon or a mixture of such hydrocarbon-adsorptive adsorbents, and suggests that activated carbon should be used carefully so as not to permit it to come out of the spacers because its color is unusual.
In addition to the aforesaid absorbing property in a system containing both water vapor and an organic solvent vapor, adsorbents for multilayer glass structures present the problem of giving off dust. Zeolite, activated carbon, etc. are liable to yield dust, although to varying degrees, when subjected to vibration, etc. imparted during the transportation and setting of multilayer glass structures or during their use as windowpanes. Unfortunately, the dust comes into the spaces between the glass sheets through adsorbing openings provided in the spacers, and adheres to the glass surfaces to reduce vision or form a nucleus that accelerates fogging.
Certainly, some proposals have previously been made as to adsorbents for multilayer glass structures, but to the present inventors best knowledge almost nothing has been proposed about the prevention of such dust occurrence.